Update {LinkEndpoint,NetworkEndpoint}#WritePacket to take a VectorisedView

Makes it possible to avoid copying or allocating in cases where DeliverNetworkPacket (rx)
needs to turn around and call WritePacket (tx) with its VectorisedView.

Also removes the restriction on having VectorisedViews with multiple views in the write path.

PiperOrigin-RevId: 211728717
Change-Id: Ie03a65ecb4e28bd15ebdb9c69f05eced18fdfcff

1 files changed, 5 insertions, 13 deletions

diff --git a/pkg/tcpip/transport/tcp/snd.go b/pkg/tcpip/transport/tcp/snd.go
index e4fa89912..284e720c6 100644
--- a/pkg/tcpip/transport/tcp/snd.go
+++ b/pkg/tcpip/transport/tcp/snd.go
@@ -270,7 +270,7 @@ func (s *sender) updateMaxPayloadSize(mtu, count int) {
 
 // sendAck sends an ACK segment.
 func (s *sender) sendAck() {
-	s.sendSegment(nil, flagAck, s.sndNxt)
+	s.sendSegment(buffer.VectorisedView{}, flagAck, s.sndNxt)
 }
 
 // updateRTO updates the retransmit timeout when a new roud-trip time is
@@ -305,7 +305,7 @@ func (s *sender) resendSegment() {
 
 	// Resend the segment.
 	if seg := s.writeList.Front(); seg != nil {
-		s.sendSegment(&seg.data, seg.flags, seg.sequenceNumber)
+		s.sendSegment(seg.data, seg.flags, seg.sequenceNumber)
 	}
 }
 
@@ -419,7 +419,7 @@ func (s *sender) sendData() {
 			segEnd = seg.sequenceNumber.Add(seqnum.Size(seg.data.Size()))
 		}
 
-		s.sendSegment(&seg.data, seg.flags, seg.sequenceNumber)
+		s.sendSegment(seg.data, seg.flags, seg.sequenceNumber)
 
 		// Update sndNxt if we actually sent new data (as opposed to
 		// retransmitting some previously sent data).
@@ -642,7 +642,7 @@ func (s *sender) handleRcvdSegment(seg *segment) {
 
 // sendSegment sends a new segment containing the given payload, flags and
 // sequence number.
-func (s *sender) sendSegment(data *buffer.VectorisedView, flags byte, seq seqnum.Value) *tcpip.Error {
+func (s *sender) sendSegment(data buffer.VectorisedView, flags byte, seq seqnum.Value) *tcpip.Error {
 	s.lastSendTime = time.Now()
 	if seq == s.rttMeasureSeqNum {
 		s.rttMeasureTime = s.lastSendTime
@@ -653,13 +653,5 @@ func (s *sender) sendSegment(data *buffer.VectorisedView, flags byte, seq seqnum
 	// Remember the max sent ack.
 	s.maxSentAck = rcvNxt
 
-	if data == nil {
-		return s.ep.sendRaw(nil, flags, seq, rcvNxt, rcvWnd)
-	}
-
-	if len(data.Views()) > 1 {
-		panic("send path does not support views with multiple buffers")
-	}
-
-	return s.ep.sendRaw(data.First(), flags, seq, rcvNxt, rcvWnd)
+	return s.ep.sendRaw(data, flags, seq, rcvNxt, rcvWnd)
 }